Police say the bus in Monday’s crash was carrying 37 students when its driver, 24-year-old Johnthony Walker, lost control of the vehicle and swerved off the roadway — striking a telephone pole and then a tree.

Twelve children were initially hospitalized following the wreck, including six in intensive care. The five students who were killed ranged in age from 6 to 10.

The bus was not equipped with seat belts, as Tennessee is not one of the six U.S. states that requires them on buses over 10,000 pounds.

The instillation and use of seat belts on school buses, while not widely adopted, has recently been promoted by federal authorities.

Lawmakers and others have said the cost of such a move would be restrictive, and some bus drivers worry they may trap students in an emergency, such as a fire. But the upside, government safety experts say, is absolute.

“The position of the National Highway Traffic Safety Administration is that seat belts save lives,” the NHTSA’s Mark Rosekind said in November 2015, according to ABC News.

“The children are protected like eggs in an egg carton — compartmentalized, and surrounded with padding and structural integrity to secure the entire container,” the Council’s website says. “The seat backs are raised and the shell is reinforced for protection against impact.”

But then in 2015, Rosekind, on behalf of the NHTSA, came out in favor of three-point lap and shoulder belts on buses.

“I don’t deny that this is a challenge,” Rosekind has said, according to the Associated Press. “But I want us to concentrate on this simple basic statement: School buses should have seat belts. Period. It should be utterly uncontroversial — there is no question that seat belts offer improved safety.”

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Rosekind later clarified that while there is no federal mandate for safety belts on school buses, his agency was in the process of working to get one instated.

“We’re gonna start everything — from research to looking for funds — to figure out how to make this happen,” he said. “The sooner we get this done, the more lives we can protect, the more injuries we can prevent.”

The National Transportation Safety Board has also recommended seat belts for newly purchased school buses, according to the AP.

Opponents of a seat belt mandate argue that it would be too costly to install them nationwide (federal agencies have estimated the cost to be between $7,000 and $10,000 per bus) and point to the fact that while school bus crashes are fairly common, fatalities resulting from these crashes are rare.

What’s more, according to the AP, a National Education Association survey of bus drivers found some express concerns that students who were panicked or disoriented in an emergency may become trapped by a seat belt (and that it would be basically impossible to ensure every student was using them).

Chattanooga Fire Department members work the scene of a fatal elementary school bus crash in Chattanooga, Tennessee, on Monday.

While nearly 500 kids and teens die in car collisions during school travel hours each year, only about four are killed while riding on school buses during those same hours, according to a 2014 report by the NHTSA.

Still, the NHTSA says the addition of seat belts could reduce this number even further. CNN highlights a non-fatal 2014 school bus crash in Anaheim, California, in which the circumstances were very similar to the Chattanooga crash — except that the bus’s passengers were wearing seat belts — to support this theory.

The NTSB noted that the proper use of seat belts by the students involved in this week’s crash reduced the severity of their injuries. But officials there have not yet said if seat belts would have prevented fatalities entirely, according to the AP.

The debate — previously raised and tabled in Tennessee — has been reignited. The state’s governor, Bill Haslam, told reporters that he wants to have a wide-ranging discussion about school bus safety following the crash, according to the AP.

“Anybody who saw anything of the Chattanooga situation yesterday, your heart is broken. It’s a tragic situation where you have little kids involved,” he said. “I think that’s part of our job to come back and say, ‘Are we doing everything we can to ensure safety on school buses?’ ”